Data communication is commonly implemented on a communication channel having multiple parallel communication links. Data words having multiple bits are transmitted over the channel, with each bit being transmitted on a single link. The width of the communication channel is typically expressed in terms of the number of communication links in the channel and, therefore, the number of bits in a data word. That is, a channel which is eight links wide will carry eight-bit data words.
Communication on the channel can often be impaired by the failure of one or more of the communication links. Such failures can include excessive noise in the link or lack of continuity caused by a break in a cable. Because even a single link failure can result in a total loss of communication on the channel, communication systems typically monitor each link for failures. When a failure is discovered, the system takes a corrective action. In most systems, this involves switching the communication from the faulty channel to a redundant spare channel having a complete set of communication links. The channel having the faulty link is left unused while communications continue on the new redundant channel.